Republicans will tell you, “it only illegal if you get caught” so aside from that, unless the jammer says on the side sticker, “this is a cell phone jammer”, the most you are doing is violating part 15 and part 16 of the FCC Rules, a “minor infraction” called Interference. <p>So if you want to conk out a single phone, at a single time, that’s one thing, however running a system 24/7 is intent, and then your in trouble. <p>Low power devices, however, can block cell phones and still meet the regulation parts 15 and 16 by not interfering out side your domain. <p>Also make sure your lawyers retainer is paid in full.

schwarz,<p>Screening the store to prevent cell phone signals getting in or out, would be more effective (more than one carrier in town?), and 100% legal because you're not transmiting aannyytthhiinngg.<p>Grounded screen or foil on walls and plastered/painted over. Metalized mylar window tint cuts signal through the front display windows.<p>Jamming is bad news. You would probably need 3 or 4 jamming transmitters on different frequencies to block adjoining cell sites. (Jam the control channel of the nearest cell site, and a phone would simply switch to the next nearest.)<p>Even though your jamming transmitters would be MUCH closer to the phones in your shop than the cell site, the transmit jamming power needed would be illegal. (I think there is a Murphy's Law about accidental interferance being more effective than intensional interferance )<p>------------------------------------
Mike,<p>Jamming is transmission of a signal to prevent use of a frequency, channel or band, for communication by someone else. Examples can prob be found in Cold War history of Voice Of America.<p>Military aircraft also do their best to JAM missle site RADAR.<p>Cheers,

As an alternative to jamming I'm wondering if it would be helpful to simply detect the presence of a cell phone and thereby set off some kind of notifier to warn the user. Seems like I read that there was a way of doing this by detecting signals that a cell phone sends out periodically to keep "logged in" to the service.

Schwarz,
I just pray that I'm never in a store with a "jammer" while some looney-tunes comes in and opens up with an uzi. Disrupting 911 service could (maybe) open you up to some serious liability.
Oh yeah, this techno-nut (me) doesn't even own a leash - whoops I meant cell phone. It better not interfere with my 2-meter though!!!
Respectfully,
Dave

As Dale suggested, Shielding incoming signals is easier, cheaper and more legal than jamming. (Well, installation could be impractical)<p>So long as you provided a land line in the store or payphone, noone could argue you deprived them of access to 911 services if needed (not a law but a possible civil concern)<p>I can't imagine why a store owner wouldn't want phones around. So many times I have called home from a store to ask "Do we need some of this?" The answer usually results in me spending more $.<p>FYIhttp://wireless.fcc.gov/services/cellul ... mming.html<p>[ March 24, 2005: Message edited by: haklesup ]</p>

"I can't imagine why a store owner wouldn't want phones around. So many times I have called home from a store to ask "Do we need some of this?" The answer usually results in me spending more $."<p>Agreed!

Our local theater spends 10 or 15 seconds on a "turn off your cell phones and pagers" clip. Why? In that metal building, my cellular phone enters a "quiet zone" of zero signal, no calls out or in. In fact, it's so quiet that even my battery charge indicator starts to suck down.<p>Dean

To discourage people from using cellphones in theatres or cinemas the operators could interrupt the performance and put it on hold for 5 minutes every time a 'phone rings.
The selfish practice, at least in those locales, may then die out.

It wouldn't be difficult or expensive to make direction finders for cellular telephones. If one or two store staff have them and let the offending parties know that unnecessary radio traffic is frowned upon, then a greater effect is obtained- people will know you can hear their signals, let them assume their conversations are understood.